Flower formation is indicated by a ‘+’, no flower formation by a ‘-‘.1. Long day, i.e. 16 h of light, 8 h of darkness: the long-day plant flowers, the short-day plant is vegetative.
2. Short day, i.e. 8 h of light and 16 h of darkness: the long-day plant is vegetative, the short-day plant flowers.
3. The long darkness of the short day is interrupted by bright red light: the Long-day plant flowers, the short-day plant is vegetative.
4. Like (3), but immediately after the exposure to bright red light are the plants exposed to dark red light. The bright red effect is neutralized. As a consequence stays the long-day plant vegetative and the short-day plant flowers. (A. LANG, 1984)